1. Field of the Invention
The present invention relates in general to a marine propulsion system, and more particularly to a transmission of an outboard drive.
2. Description of Related Art
Several outboard drives of a marine watercrafts now employ counter-rotating propeller systems operated by forward/neutral/reverse transmissions. Such propulsion systems are common in both outboard motors and in outboard drive units of inboard/outboard motors.
Prior transmissions used with counter-rotating propeller systems typically include a drive pinion and a pair of oppositely rotating driven bevel gears. Each driven gear includes a hub that is journaled within a lower unit of the outboard drive by a bearing assembly.
A front dog clutch of a dual clutch assembly of the transmission is interposed between the pair of oppositely rotating gears. The front dog clutch is moved between positions in which the clutch engages the gears. In this manner, the front dog clutch selectively couples an inner propeller shaft to one of the driven gears to rotate a first propeller in either a forward or a reverse direction.
The transmission also includes a second dog clutch that is positioned on the rear side of the rear driven gear hub. The rear clutch selectively engages corresponding teeth formed on the rear side of the hub of the rear gear. The rear clutch also is coupled to a hollow outer propulsion shaft which is drives when engaged with the rear gear.
A pair of spaced bearing assemblies commonly journal the hollow outer propeller shaft within the lower unit. The bearings assemblies lie within a bearing carrier which extends to the rear side of the transmission. A first bearing assembly of the pair typically supports the front end of the outer propeller shaft at a position directly behind the rear driven gear. The second bearing assembly supports the outer propeller shaft at the rear end of the bearing carrier.
In many lower unit arrangements, the inner shaft extends through the hollow outer propeller shaft and passes through both the front and rear driven gears. An actuator mechanism or the housing of the lower unit commonly support the front end of the inner propeller shaft and a needle bearing assembly supports the inner shaft toward the rear end of the outer propeller shaft. The inner shaft generally is not support at any other points along its length.